A bit of a head-scratcher, this one. No papers (again) today because of the snow, so glad to get the coffee on and tackle the treasure hunt. I think I've got all the letters, but much staring and much coffee have not come up with the earthwork yet. I'll get back to you.....
I had expected it to be much closer to town 2 from the clue! OH too used the PM rather than the house and I misread the letters from the archbishop occasionally, I spent my professional telling students to read the question properly!